The field of invention relates generally to micro-fabrication of structures. More particularly, the present invention is directed to a functional patterning material suited for use in imprint lithographic processes to form optical components.
Optical communication systems include numerous optical devices, such as planar optical slab waveguides, channel optical waveguides, rib waveguides, optical couplers, optical splitters, optical switches, micro-optical elements and the like. Many of these optical devices are employed using standard photolithographic processes. As a result, many photopolymers have been developed. The photopolymers, such as acrylate materials, are light sensitive to facilitate recordation of a pattern therein. Furthermore, the photopolymers must demonstrate suitable operational and process characteristics. For example, it is desired that the photopolymers have good clarity and low birefringence over a range of temperatures. As a result, the thermal stability of the photopolymers is an important factor and should be such that the probability of color changes in the photopolymers is minimized during prolonged operation. Additionally, the photopolymers should withstand stresses so as not to crack during the baking process or during use. Finally, maximizing the miniaturization of the optical devices is desired. Recent advances in micro-fabrication techniques, have showed promising results in miniaturizing optical devices.
An exemplary micro-fabrication technique, commonly referred to as imprint lithography, is shown in U.S. Pat. No. 6,334,960 to Willson et al. Willson et al. disclose a method of forming a relief image in a structure. The method includes providing a substrate having a transfer layer. The transfer layer is covered with a polymerizable fluid composition. A mold makes mechanical contact with the polymerizable fluid. The mold includes a relief structure, and the polymerizable fluid composition fills the relief structure. The polymerizable fluid composition is then subjected to conditions to solidify and polymerize the same, forming a solidified polymeric material on the transfer layer that contains a relief structure complimentary to that of the mold. The mold is then separated from the solid polymeric material such that a replica of the relief structure in the mold is formed in the solidified polymeric material. The transfer layer and the solidified polymeric material are subjected to an environment to selectively etch the transfer layer relative to the solidified polymeric material such that a relief image is formed in the transfer layer. The time required and the minimum feature dimension provided by this technique is dependent upon, inter alia, the composition of the polymerizable material. However, Willson et al. does not disclose material suitable for use in forming optical devices employed in communication systems that may be formed using imprint lithography.
It is desired, therefore, to provide techniques to form optical devices using imprint lithographic processes.